Contact arrangement for a high-voltage circuit breaker

ABSTRACT

A contact arrangement for a high-voltage switching apparatus includes two hollow contact pieces across which a switching member of the switching apparatus is movable to electrically join and separate the contact pieces. The contact pieces are mutually adjacent so as to cause the respective end-faces thereof to define a gap when the switching member is moved to the open position. At least one of the contact pieces includes a contact member having an end-portion at the region of the end-face of the one contact piece. A metallic annular member made of arcresistant material is supportably mounted on the contact member at the end-portion thereof. A nozzle-shaped graphite electrode is electrically joined to the contact member. The contact member and the annular metal member conjointly surround the graphite electrode.

United States Patent Schramm et al.

AvAILABI-E cow [451 July 15,1975

CONTACT ARRANGEMENT FOR A HIGH-VOLTAGE CIRCUIT BREAKER Inventors: Heinz-H. Schramm; Ernst Slamecka, both of Berlin, Germany Assignee: Siemens Aktiengesellschaft, Munich, Germany Filed: July 6, 1973 Appl. No.: 376,942

Foreign Application Priority Data July 7, 1972 Germany 2234067 U.S. Cl 200/148 R; ZOO/146 ZOO/275; ZOO/14.7 R; ZOO/269 Int. Cl. HOlh 33/82 Field of Search 200/146 R, R, 148 G, 200/166 C, 147 R References Cited UNITED STATES PATENTS 12/1944 Journeaux 200/146 R 12/1944 Amer et al.

10/1965 Gonek et a1. l/1974 Beier 200/148 R FOREIGN PATENTS OR APPLICATIONS 525,244 8/1940 United Kingdom 200/148 0 Primary Examinen-Ro'bett S. Macon Attorney, Agent, or FiMt Kenyon & Kenyon Reill Carr & Chapin I 1 v 57 'AiisTRAcT A contact arrangement for a high-voltage switching apparatus includes hollow contact pieces across which a switching member of the switching apparatus is movable to electrically join and separate the contact pieces. The contact pieces are mutually adjacent so as 7 Claims, 7 brawing Figures l; l ///V// illi/11111111111.

pmmg'm 15 ms 3 8 95201 SHEET 1 Fig. 5 f Fi 7 3,4 9 14 1 0 3,4 9 1 4 10 CONTACT ARRANGEMENT FOR A HIGH-VOLTAGE CIRCUIT BREAKER BACKGROUND OF THE INVENTION From Deutsche Auslegeschrift 1,088,580, a highvoltage power circuit breaker is known wherein the arc drawn between the burnoff rings of two contacts is moved under the influence of magnetic forces within a gaseous medium. Themagnetic field generated by two coils, through which the arc current flows, here assists the quenching of the arc at the zero crossing of the alternating current.

In high-voltage switching gear, particularly highvoltage power circuit breakers, which are constructed for currents of 60 KA for example, the physical dimensions are determined by the current-carrying parts. If magnetic blasting coils as in the circuit breaker known from the Deutsche Auslegeschrift 1,088,580 are used, more space is required, which is undesirable in some cases.

From the Czechoslovakian Patent 419,690, a contact arrangement for pressurized-gas circuit breakers is known wherein the power switching gap consists of two coaxial tubular nozzles which are arranged at a fixed distance from each other and are provided with slots. Through the radial slots in the nozzle-shaped switching contacts, a magnetic force is exerted on the arc and drives the are into the interior of the hollow contacts; this force being in addition to the gas flow developed during the breaker-opening operation.

The slots in the end-faces of the tubular nozzles can limit the current-carrying capacity of the contacts in a detrimental manner and require expensive manufacturing procedures.

SUMMARY OF THE INVENTION The invention relates to a contact arrangement for a pressurized gas-insulated high-voltage switching apparatus, and in particular, a high-voltage power circuit breaker. The contact arrangement can, for example, include two hollow contact pieces which in the closed position of the apparatus are connected with each other. The contact pieces have respective end-faces which define a gap when the breaker is in the open position. At the end-faces, the contact pieces carry respective annular metallic members of arc-resistant material. In such a configuration, the arc drawn between the annular members is blasted at the beginning of the electrical separation by the pressurized gas in such a manner that the arc is driven into the interior of the contact pieces.

In switching apparatus wherein the arc is blasted by pressurized-gas, it is an object of the invention to develop a force supplementary to the gas blast which is directed toward the interior of the contact pieces and which is developed by magnetically blasting the arc with simple means.

According to the invention, the foregoing object is achieved by the arrangement that the contact member and the annular member surround an annular graphite electrode, which is connected with the contact member in an electrically conducting manner. In the invention, the difference in the conductivity of the contact member, which as a rule consists of copper, and the graphite electrode is utilized for a current loop which drives the arc into the interior of the contact piece. This current loop arises because of the are which sets on the graphite electrode and is driven toward the axis of the electrode because the current tends to flow at all times along the shortest path to the surrounding hollow contact member in order to keep the voltage drop within the graphite electrode small.

In a preferred embodiment, the graphite electrode is connected with the contact member in the vicinity of the endface. By means of the electrical connection of the graphite electrode in the area of the end-face of the contact piece, there is obtained an enhancement of the loop formation, This loop formation can be aided further by the provision that the graphite electrode is sup ported by the contact member with the interposition of a layer of insulating material therebetween, this layer being arranged so as to extend up to the region of the end-face of the contact piece. As insulation material, polytetrafluoroethylene is especially to be considered.

In another preferred embodiment, the contact piece can include a copper tube and can be provided with an annular member of tungsten-copper. The copper tube and the annular member can be advantageously joined on the inner side by a steel tube which carries the graphite electrode. The steel tube forms here a mounting for the graphite electrode which is advantageous for mechanical reasons.

In a subsidiary embodiment, the contact piece consists of a steel tube with an outer copper layer.

A high-voltage circuit breaker can be provided with a contact arrangement wherein the hollow contact pieces are arranged so as to be stationary and. in the breaker-closed position, these contact pieces are electrically joined at their outer surfaces by a movable bridging contact member. In such a breaker, because the contact piece and the annular member surround the nozzle-shaped graphite electrode and the graphite electrode therefore does not project from the end-face of the hollow contact piece, the advantage is obtained that the surfaces of the contact fingers of the movable bridging contact member which glide over the outer surfaces of the contact pieces are protected from contamination by the graphite material. In this connection, it is ensured that by the relatively high resistivity of graphite, increased contact resistance between the contact fingers and the stationary contact pieces is effectively avoided, so that the current and for intermittent operation is not impaired by graphite deposits.

Although the invention is illustrated and described herein as a contact arrangement for a high-voltage circuit breaker, it is nevertheless not intended to be limited to the details shown, since various modifications may be made therein within the scope and the range of the claims. The invention, however, together with additional objects and advantages will be best understood from the following description and in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a schematic diagram partially in section of the pertinent portion of the switching chamber of a high-voltage power circuit breaker of the compressedgas type. This view shows the contact pieces in outline. The left half of the diagram shows the bridging contact member in the open position and the right half shows the bridging member in the closed position.

FIGS. 2 to 4 each show a longitudinal half-section of a preferred embodiment of one of the contact pieces of the contact arrangement according to the invention.

These views further show the position and contour of the are at different points of the contact piece at different times during the breaker opening operation.

FIG. illustrates another embodiment of the invention wherein the contact arrangement is provided with an intermediate layer of insulating material.

FIG. 6 illustrates another embodiment of the contact arrangement of the invention wherein the contact piece is provided with a steel tube.

FIG. 7 illustrates still another embodiment of the contact arrangement according to the invention wherein the contact piece of FIG. 6 is provided additionally with an intermediate layer of insulating material.

DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION The high-voltage power circuit breaker according to FIG. 1 is constructed as a pressurized-gas circuit breaker. As shown schematically in FIG. 1 in a crosssection, the breaker includes a switching chamber 1 for example, as a porcelain tube. The interior 2 is filled with a gas as the quenching and insulating medium, particularly with sulfur hexafluoride. In the interior 2, two contact pieces 3 and 4 are arranged on a common axis so as to be mutually adjacent and thereby define with their respective end-faces 5 a gap 6. In the closed position of the breaker shown to the right of the center line 7, the two contact pieces 3 and 4 are connected with each other in an electrically conducting manner; whereas, to the left of the center line 7, the breaker is shown in its open position. For the open position, the circuit breaker here assumes a position wherein the bridging contact member 8 frees the gap 6. The contact pieces 3, 4 are made hollow to direct away the switching gases.

In FIGS. 2 to 4, a part of a contact piece 3 and/or 4 is schematically shown in a half-cross section. The contact piece 3, 4 consists of a hollow contact member 9, which is provided in the region of the end-face 5 with an annular, metallic member of arc-resistant material such as tungsten-copper for example. The contact member 9 and the annular member 10 surround and embrace a nozzleshaped graphite electrode 11 which directs away the hot switching gases produced in the interruption process and guides the are 12.

The are occurring during the interruption process sets down at the end-face on the graphite electrode 11 and is forced to form a loop because of the large difference in conductivity between the contact member 9 made of copper and the electrode 11 made of graphite; under the influence of the magnetic field generated, this loop exerts an inwardly directed force on the arc. As the foot point of the arc travels into the interior of the graphite electrode 11, the course of current flow in the graphite electrode also changes, so that a more pronounced contour is imparted to the loop in FIG. 3. In this manner, the arc 12 is driven into a position shown in FIG. 4 in which it can be quenched most readily.

FIG. 5 shows a somewhat different embodiment of the contact 3, 4 wherein the graphite electrode 11 is supported by the contact member 9 with the interposition of a layer of insulating material 13. The layer 13 may consist, for example, of polytetrafluorethylene. Because of the fact that in this embodiment the graphite electrode 11 is in electrical contact with the contact member 9 only at the end-face, the loop effect of the current and thereby the magnetic blast can be increased in the phase of the arc development corresponding to FIG. 4.

In the embodiments described above, the contact member 9 consists of copper tubing which is provided with an annular member 10 of tungsten-copper.

In some cases it may be advantageous to surround the graphite electrode 11 with a steel tube 14 as a mounting prior to insertion into the contact member 9. The steel tube 14 carries the graphite electrode 11 and engages it preferably with a friction fit. The steel tube can be pressed into the contact member 9. The direction of the arc in the embodiment according to FIG. 6 corresponds to the direction of the arc in the contact piece according to FIGS. 2 to 4.

FIG. 7 illustrates a further embodiment of a contact piece 3 and/or 4, wherein the graphite electrode is surrounded by a steel tube 14 with a friction fit and with the interposition of an insulating layer 13. The tube 14 is in turn connected with the contact 9 consisting of copper. The direction of the arc and the development of the current paths in the contact piece 3, 4 which form while the arc is burning, correspond to the embodiment of FIG. 5.

It is further possible that the contact member be made ofa steel tube and be provided with an outer copper layer. The copper layer in this embodiment replaces the copper tube 9 and the steel tube serves as the carrier for the annular member 10 consisting of tungsten-copper.

What is claimed is:

l. A contact arrangement for a high-voltage switching apparatus of the compressed-gas type such as a power circuit breaker or the like having a switching member movable between open and closed positions, the contact arrangement comprising: two hollow contact pieces across which the switching member is movable to electrically join the contact pieces in the closed position and to electrically separate the contact pieces in the open position, said contact pieces having respective end-faces and being mutually adjacent so as to cause said end-faces to define a gap when the switching member is moved to the open position, at least one of said contact pieces including a contact member having an end-portion at the region of said end-face of said one contact piece, a metallic annular member made of arc-resistant material supportably mounted on said contact member at said end-portion thereof, and a nozzle-shaped graphite electrode electrically joined to said contact member, said contact member and said annular metal member conjointly surrounding and embracing said graphite electrode. I

2. The contact arrangement of claim 1, said graphite electrode being joined to said contact member at the end-face region of said one contact piece.

3. The contact arrangement of claim 1 comprising a layer of insulating material disposed intermediate said graphite electrode and said contact member, said layer extending up to the region of said end-face so as to cause said graphite electrode to be electrically joined to said contact member only at said region of said endface.

4. The contact arrangement of claim 3, said insulating material being polytetrafluorethylene.

5. The contact arrangement of claim 1, said contact member being a copper tube, said metallic annular 6 member being supportably mounted on said copper surface; said graphite electrode being supportably tube and being made of tungsten-copper. mounted i id Steel tube 7. The contact arrangement of claim 1, said contact member consisting of a steel tube having an outer layer 

1. A contact arrangement for a high-voltage switching apparatus of the compressed-gas type such as a power circuit breaker or the like having a switching member movable between open and closed positions, the contact arrangement comprising: two hollow contact pieces across which the switching member is movable to electrically join the contact pieces in the closed position and to electrically separate the contact pieces in the open position, said contact pieces having respective end-faces and being mutually adjacent so as to cause said end-faces to define a gap when the switching member is moved to the open position, at least one of said contact pieces including a contact member having an end-portion at the region of said end-face of said one contact piece, a metallic annular member made of arc-resistant material supportably mounted on said contact member at said end-portion thereof, and a nozzle-shaped graphite electrode electrically joined to said contact member, said contact member and said annular metal member conjointly surrounding and embracing said graphite electrode.
 2. The contact arrangement of claim 1, said graphite electrode being joined to said contact member at the end-face region of said one contact piece.
 3. The contact arrangement of claim 1 comprising a layer of insulating material disposed intermediate said graphite electrode and said contact member, said layer extending up to the region of said end-face so as to cause said graphite electrode to be electrically joined to said contact member only at said region of said end-face.
 4. The contact arrangement of claim 3, said insulating material being polytetrafluorethylene.
 5. The contact arrangement of claim 1, said contact member being a copper tube, said metallic annular member being supportably mounted on said copper tube and being made of tungsten-copper.
 6. The contact arrangement of claim 5 wherein said copper tube and said metallic annular member conjointly define an inner surface, and wherein said one contact piece comprises a steel tube joined to said copper tube and said metallic annular member at said inner surface; said graphite electrode being supportably mounted in said steel tube.
 7. The contact arrangement of claim 1, said contact member consisting of a steel tube having an outer layer of copper. 